Dexamethasone-loaded poly(epsilon-caprolactone) intravitreal implants: a pilot study.

PURPOSE: Poly(epsilon-caprolactone) (PCL) is a biodegradable and biocompatible polymer that presents a very low degradation rate, making it suitable for the development of long-term drug delivery systems. The objective of this pilot study is to evaluate the feasibility and characteristics of PCL devices in the prolonged and controlled intravitreous release of dexamethasone. METHODS: The in vitro release of dexamethasone was investigated and the implant degradation was monitored by the percent of mass loss and by changes in the surface morphology. Differential scanning calorimetry was used to evaluate stability and interaction of the implant and the drug. The short-term tolerance of the implants was studied after intravitreous implantation in rabbit eye. Results: PCL implant allows for a controlled and prolonged delivery of dexamethasone since it releases 25% of the drug in 21 weeks. Its low degradation rate was confirmed by the mass loss and scanning electron microscopy studies. Preliminary observations show that PCL intravitreous implants are very well tolerated in the rabbit eye. CONCLUSION: This study demonstrates the PCL drug delivery systems allowed to a prolonged release of dexamethasone in vitro. The implants demonstrated a strikingly good intraocular short-term tolerance in rabbits eyes. The in vitro and preliminary in vivo studies tend to show that PCL implants could be of interest when long-term sustained intraocular delivery of corticosteroids is required.

Engineered aprotinin for improved stability of fibrin biomaterials.

Fibrin has been long used clinically for hemostasis and sealing, yet extension of use in other applications has been limited due to its relatively rapid resorption in vivo, even with addition of aprotinin or other protease inhibitors. We report an engineered aprotinin variant that can be immobilized within fibrin and thus provide extended longevity. When recombinantly fused to a transglutaminase substrate domain from α(2)-plasmin inhibitor (α(2)PI(1-8)), the resulting variant, aprotinin-α(2)PI(1-8), was covalently crosslinked into fibrin matrices during normal thrombin/factor XIIIa-mediated polymerization. Challenge with physiological plasmin concentrations revealed that aprotinin-α(2)PI(1-8)-containing matrices retained 78% of their mass after 3 wk, whereas matrices containing wild type (WT) aprotinin degraded completely within 1 wk. Plasmin challenge of commercial sealants Omrixil and Tisseel, supplemented with aprotinin-α(2)PI(1-8) or WT aprotinin, showed extended longevity as well. When seeded with human dermal fibroblasts, aprotinin-α(2)PI(1-8)-supplemented matrices supported cell growth for at least 33% longer than those containing WT aprotinin. Subcutaneously implanted matrices containing aprotinin-α(2)PI(1-8) were detectable in mice for more than twice as long as those containing WT aprotinin. We conclude that our engineered recombinant aprotinin variant can confer extended longevity to fibrin matrices more effectively than WT aprotinin in vitro and in vivo.

Evaluation of uptake and transport of cationic and anionic ultrasmall iron oxide nanoparticles by human colon cells

Nanoparticles (NPs) are in clinical use or under development for therapeutic imaging and drug delivery. However, relatively little information exists concerning the uptake and transport of NPs across human colon cell layers, or their potential to invade three-dimensional models of human colon cells that better mimic the tissue structures of normal and tumoral colon. In order to gain such information, the interactions of biocompatible ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) (iron oxide core 9-10 nm) coated with either cationic polyvinylamine (aminoPVA) or anionic oleic acid with human HT-29 and Caco-2 colon cells was determined. The uptake of the cationic USPIO NPs was much higher than the uptake of the anionic USPIO NPs. The intracellular localization of aminoPVA USPIO NPs was confirmed in HT-29 cells by transmission electron microscopy that detected the iron oxide core. AminoPVA USPIO NPs invaded three-dimensional spheroids of both HT-29 and Caco-2 cells, whereas oleic acid-coated USPIO NPs could only invade Caco-2 spheroids. Neither cationic aminoPVA USPIO NPs nor anionic oleic acid-coated USPIO NPs were transported at detectable levels across the tight CacoReady? intestinal barrier model or the more permeable mucus-secreting CacoGoblet? model.

Evaluation of uptake and transport of cationic and anionic ultrasmall iron oxide nanoparticles by human colon cells.

Nanoparticles (NPs) are in clinical use or under development for therapeutic imaging and drug delivery. However, relatively little information exists concerning the uptake and transport of NPs across human colon cell layers, or their potential to invade three-dimensional models of human colon cells that better mimic the tissue structures of normal and tumoral colon. In order to gain such information, the interactions of biocompatible ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) (iron oxide core 9-10 nm) coated with either cationic polyvinylamine (aminoPVA) or anionic oleic acid with human HT-29 and Caco-2 colon cells was determined. The uptake of the cationic USPIO NPs was much higher than the uptake of the anionic USPIO NPs. The intracellular localization of aminoPVA USPIO NPs was confirmed in HT-29 cells by transmission electron microscopy that detected the iron oxide core. AminoPVA USPIO NPs invaded three-dimensional spheroids of both HT-29 and Caco-2 cells, whereas oleic acid-coated USPIO NPs could only invade Caco-2 spheroids. Neither cationic aminoPVA USPIO NPs nor anionic oleic acid-coated USPIO NPs were transported at detectable levels across the tight CacoReady? intestinal barrier model or the more permeable mucus-secreting CacoGoblet? model.

Orthopedic implant used as drug delivery system: clinical situation and state of the research.

A partial review is proposed on the existing literature for the research performed in orthopedic implant used as drug delivery system. In the first part, an evaluation is given on the clinical need to deliver a drug in the surrounding of an implant. Secondly, a review of the clinical situation is developed for implants already used as drug delivery system. Experimental works performed for local delivery are reported. In particular, a description is given on the in vitro and in vivo studies where the implant is coated with different proteins or drugs. Finally, a conclusion is proposed on the next step in the development of orthopedic implant as drug delivery system mentioning also the industrial situation.

Synthesis of chemically functionalized superparamagnetic nanoparticles as delivery vectors for chemotherapeutic drugs.

Superparamagnetic iron oxide nanoparticles (SPIONs) are in clinical use for disease detection by MRI. A major advancement would be to link therapeutic drugs to SPIONs in order to achieve targeted drug delivery combined with detection. In the present work, we studied the possibility of developing a versatile synthesis protocol to hierarchically construct drug-functionalized-SPIONs as potential anti-cancer agents. Our model biocompatible SPIONs consisted of an iron oxide core (9-10 nm diameter) coated with polyvinylalcohols (PVA/aminoPVA), which can be internalized by cancer cells, depending on the positive charges at their surface. To develop drug-functionalized-aminoPVA-SPIONs as vectors for drug delivery, we first designed and synthesized bifunctional linkers of varied length and chemical composition to which the anti-cancer drugs 5-fluorouridine or doxorubicin were attached as biologically labile esters or peptides, respectively. These functionalized linkers were in turn coupled to aminoPVA by amide linkages before preparing the drug-functionalized-SPIONs that were characterized and evaluated as anti-cancer agents using human melanoma cells in culture. The 5-fluorouridine-SPIONs with an optimized ester linker were taken up by cells and proved to be efficient anti-tumor agents. While the doxorubicin-SPIONs linked with a Gly-Phe-Leu-Gly tetrapeptide were cleaved by lysosomal enzymes, they exhibited poor uptake by human melanoma cells in culture.

Membrane-destabilizing activity of pH-responsive cationic lysine-based surfactants: role of charge position and alkyl chain length

Many strategies for treating diseases require the delivery of drugs into the cell cytoplasm following internalization within endosomal vesicles. Thus, compounds triggered by low pH to disrupt membranes and release endosomal contents into the cytosol are of particular interest. Here, we report novel cationic lysine-based surfactants (hydrochloride salts of N¿- and N¿-acyl lysine methyl ester) that differ in the position of the positive charge and the length of the alkyl chain. Amino acid-based surfactants could be promising novel biomaterials in drug delivery systems, given their biocompatible properties and low cytotoxic potential. We examined their ability to disrupt the cell membrane in a range of pH values, concentrations and incubation times, using a standard hemolysis assay as a model of endosomal membranes. Furthermore, we addressed the mechanism of surfactant-mediated membrane destabilization, including the effects of each surfactant on erythrocyte morphology as a function of pH. We found that only surfactants with the positive charge on the ¿-amino group of lysine showed pH-sensitive hemolytic activity and improved kinetics within the endosomal pH range, indicating that the positive charge position is critical for pH-responsive behavior. Moreover, our results showed that an increase in the alkyl chain length from 14 to 16 carbon atoms was associated with a lower ability to disrupt cell membranes. Knowledge on modulating surfactant-lipid bilayer interactions may help us to develop more efficient biocompatible amino acid-based drug delivery devices.

Analysis of bioavailable arsenic in rice with whole cell living bioreporter bacteria.

A multiwell plate bioassay was developed using genetically modified bacteria (bioreporter cells) to detect inorganic arsenic extracted from rice. The bacterial cells expressed luciferase upon exposure to arsenite, the activity of which was detected by measurement of cellular bioluminescence. The bioreporter cells detected arsenic in all rice varieties tested, with averages of 0.02-0.15 microg of arsenite equivalent per gram of dry weight and a method detection limit of 6 ng of arsenite per gram of dry rice. This amounted to between approximately 20 and 90% of the total As content reported by chemical methods for the same sample and suggested that a major proportion of arsenic in rice is in the inorganic form. Calibrations of the bioassay with pure inorganic and organic arsenic forms showed that the bacterial cells react to arsenite with highest affinity, followed by arsenate (with 25% response relative to an equivalent arsenite concentration) and trimethylarsine oxide (at 10% relative response). A method for biocompatible arsenic extraction was elaborated, which most optimally consisted of (i) grinding rice to powder, (ii) mixing with an aqueous solution containing pancreatic enzymes, (iii) mechanical shearing, (iv) extraction in mild acid conditions and moderate heat, and (v) centrifugation and pH neutralization. Detection of mainly inorganic arsenic by the bacterial cells may have important advantages for toxicity assessment of rice consumption and would form a good complement to total chemical arsenic determination.

Improved growth with bioabsorbable sutures in both high- and low-pressure zones.

BACKGROUND: Compromised growth after operation remains a significant problem in the cardiovascular field. Some benefit of absorbable suture materials has been demonstrated for arterial anastomoses. However, for the low-pressure zone, few data are available. METHODS: To assess growth in high- versus low-pressure zones we transected the abdominal aorta (high-pressure zone) as well as the inferior vena cava (low-pressure zone) in 10 young mongrel dogs using for reanastomosis 7-0 nonabsorbable versus absorbable running sutures in random order. RESULTS: All animals survived and were evaluated over 12 months including body weight (gain, 212% +/- 45% for nonabsorbable versus 218% +/- 8% for absorbable; not significant), angiography, and, after elective sacrifice, detailed studies of aorta and vena cava. Systematic complication of angiographic data at 12 months showed at the suture level an area of 13.8 mm2 for nonabsorbable versus 24.3 +/- 14.4 mm2 for absorbable sutures in the high-pressure zone as compared with 12.9 +/- 4.9 mm2 for nonabsorbable versus 25.3 +/- 15.4 mm2 for absorbable sutures in the low-pressure zone. Residual lumen, calculated as a function of the area above and below the suture, accounted for 35% +/- 10% for nonabsorbable versus 92% +/- 12% for absorbable sutures (p < 0.001) in the high-pressure zone as compared with 37% +/- 13% for nonabsorbable versus 75% +/- 15% for absorbable sutures (p < 0.003) in the low-pressure zone (high versus low, not significant). Poststenotic dilatation accounted for 199% +/- 22% for nonabsorbable versus 126% +/- 43% for absorbable sutures (p < 0.01) in the high-pressure zone. In the low-pressure zone, poststenotic dilatation remained below the inflow area, and the residual poststenotic lumen accounted for 52% +/- 14% for nonabsorbable versus 77% +/- 16% for absorbable sutures (p < 0.004). Macroscopic, light, and scanning electron microscopic studies confirmed different growth patterns in high- versus low-pressure zones. CONCLUSIONS: Aortic narrowing resulted in poststenotic dilatation and unrestricted outflow path (hourglass-type stenosis). Caval narrowing was followed by restriction of poststenotic outflow path (funnel-type stenosis). Absorbable suture material allows for superior growth in both high- and low-pressure zones.

Schwann cell strip for peripheral nerve repair.

Many strategies have been investigated to provide an ideal substitute to treat a nerve gap injury. Initially, silicone conduits were used and more recently conduits fabricated from natural materials such as poly-3-hydroxybutyrate (PHB) showed good results but still have their limitations. Surgically, a new concept optimising harvested autologous nerve graft has been introduced as the single fascicle method. It has been shown that a single fascicle repair of nerve grafting is successful. We investigated a new approach using a PHB strip seeded with Schwann cells to mimic a small nerve fascicle. Schwann cells were attached to the PHB strip using diluted fibrin glue and used to bridge a 10-mm sciatic nerve gap in rats. Comparison was made with a group using conventional PHB conduit tubes filled with Schwann cells and fibrin glue. After 2 weeks, the nerve samples were harvested and investigated for axonal and Schwann cell markers. PGP9.5 immunohistochemistry showed a superior nerve regeneration distance in the PHB strip group versus the PHB tube group (> 10 mm, crossed versus 3.17+/- 0.32 mm respectively, P<0.05) as well as superior Schwann cell intrusion (S100 staining) from proximal (> 10 mm, crossed versus 3.40+/- 0.36 mm, P<0.01) and distal (> 10 mm, crossed versus 2.91+/- 0.31 mm, P<0.001) ends. These findings suggest a significant advantage of a strip in rapidly connecting a nerve gap lesion and imply that single fascicle nerve grafting is advantageous for nerve repair in rats.

Importance of polyethylene thickness in total shoulder arthroplasty: a finite element analysis.

BACKGROUND: Articular surfaces reconstruction is essential in total shoulder arthroplasty. Because of the limited glenoid bone support, thin glenoid component could improve anatomical reconstruction, but adverse mechanical effects might appear. METHODS: With a numerical musculoskeletal shoulder model, we analysed and compared three values of thickness of a typical all-polyethylene glenoid component: 2, 4 (reference) and 6mm. A loaded movement of abduction in the scapular plane was simulated. We evaluated the humeral head translation, the muscle moment arms, the joint force, the articular contact pattern, and the polyethylene and cement stress. Findings Decreasing polyethylene thickness from 6 to 2mm slightly increased humeral head translation and muscle moment arms. This induced a small decreased of the joint reaction force, but important increase of stress within the polyethylene and the cement mantel. Interpretation The reference thickness of 4mm seems a good compromise to avoid stress concentration and joint stuffing.

Antibacterial burst-release from minimal Ag-containing plasma polymer coatings.

Biomaterials releasing silver (Ag) are of interest because of their ability to inhibit pathogenic bacteria including antibiotic-resistant strains. In order to investigate the potential of nanometre-thick Ag polymer (Ag/amino-hydrocarbon) nanocomposite plasma coatings, we studied a comprehensive range of factors such as the plasma deposition process and Ag cation release as well as the antibacterial and cytocompatible properties. The nanocomposite coatings released most bound Ag within the first day of immersion in water yielding an antibacterial burst. The release kinetics correlated with the inhibitory effects on the pathogens Pseudomonas aeruginosa or Staphylococcus aureus and on animal cells that were in contact with these coatings. We identified a unique range of Ag content that provided an effective antibacterial peak release, followed by cytocompatible conditions soon thereafter. The control of the in situ growth conditions for Ag nanoparticles in the polymer matrix offers the possibility to produce customized coatings that initially release sufficient quantities of Ag ions to produce a strong adjacent antibacterial effect, and at the same time exhibit a rapidly decaying Ag content to provide surface cytocompatibility within hours/days. This approach seems to be favourable with respect to implant surfaces and possible Ag-resistance/tolerance built-up.